Halogenated polymeric compositions containing zinc borate

ABSTRACT

Halogenated polymeric compositions containing a fire retarding amount of zinc borate of the formula 2ZnO.3B2O3.3.5H2O.

United State:

Woods et al.

HALOGENATED POLYMERIC COMPOSITIONS CONTAINING ZINC BORATE Inventors:William G. Woods, Fullerton, Joseph v G. Whiten, Dublin, Nelson P. Nies,Laguna Beach, all of Calif.

Assignee: United States Borax & Chemical Corporation, Los Angeles,Calif.

Filed: March 5, 1971 Appl. No.: 121,603

Related US. Application Data Continuation-impart of Ser. No. 725,169,April 29, 1968, abandoned.

US. Cl. ..260/28, 260/285 D, 106/15 FP Int. Cl. ..C08h 51/04, C08f45/04, C09d 5/18 Field of Search ..260/28, DIG. 24, 28.5 D, 40,

260/41 R; 106/15 FP; 23/55, 59

. 1 Feb. 27, 1973 Industrial & Engineering Chemistry, August, 1949,pages 1742-1749, Weisberg et al.

Primary Examiner--Morris Liebman Assistant Examiner-S. L. FoxAttorney-James R. Thornton [5 7 ABSTRACT Halogenated polymericcompositions containing a fire retarding amount of zinc borate of theformula 2Z- nO-3B,O3.5H p.

14 Claims, No Drawings IIALOGENATED POLYMERIC COMPOSITIONS CONTAININGZINC BORATE RELATED APPLICATIONS This is a continuation-in-part of ourcopending application Ser. No. 725,169 filed Apr. 29, 1968 and nowabandoned.

BACKGROUND AND SCOPE This invention relates to novel fire retardingpolymeric compositions, and to methods for rendering such polymericmaterials fire retardant. Polymeric materials are being widely usedtoday in applications where it is highly desirable that the polymericcompositions be fire retardant and flame resistant. Prior art attemptsto impart fire resistance to polymers by the use of additives have oftenadversely affected other desirable properties of the polymer.

The search for compounds or compositions of matter as flame retardantsfor polymers has been intensively conducted industrially. The use ofcompounds containing phosphorus and/or nitrogen as flame retardantadditives for some polymers has been recognized, as has been the use ofvarious halogenated materials, such as chlorinated paraffin wax, andantimony compounds such as antimony oxide, and mixtures thereof. Thedisadvantage, however, in regard to the known prior art materials whichhave been used as flame retardants has been the fact that generally alarge amount of the additive must be incorporated into the polymer tomake it sufficiently flame retardant. In addition, the prior art flameretardant additives frequently do not stand up to processing conditionsand will in some cases separate out from the resin after incorporation.The search for fire retarding adjuvants is important because it isessential that many resin compositions have relatively high resistanceto burning if they are to be commercially utilizable. Further, theresins must be capable of enduring heat without deterioration and beable to resist fire and flame. Especially, materials used in conjunctionwith electricity must be able to resist ignition or deterioration byheat and sparks. Also, it is quite essential that structural materialshave excellent flame retardance. As the requisite degree of flameretardance is achieved, it is essential that the other desirablequalities of the resinous material be preserved or enhanced. In

' addition to the preservation of the mechanical properties of thepolymer, it is desirable that the color should not be adverselyaffected.

BRIEF DESCRIPTION It has now been discovered that a zinc borate having aspecific water of hydration which, when added to halogenated polymers,produces excellent flame retarding compositions without stronglyadversely affecting other physical properties of the polymer.

The compound of the present invention is a zinc borate having theformula: 2ZnO3B O '3.5H O. Due to slight amounts of impurities andanalytical errors, the H content can vary between about 3.3 and 3.7 butit will generally average about 3.5H O. It will be appreciated that thiszinc borate has a much lower degree of water of hydration thanpreviously utilized zinc borates. Due to the low amount of water ofhydration there is less problem with this zinc borate when it is addedto polymeric material with regard to formation of bubbles than withother zinc borates or other inorganic material during processing,molding and curing. When the specific zinc borate is added to polymers,fire resistance of the polymers is greatly improved while the otherphysical properties of the polymers are not deteriorated.

A method for producing the zinc borate of low hydration is set forth incopending application of Nies et al., Ser. No. 648,968, filed June 26,1967, now US. Pat. No. 3,549,316.

The invention, therefore, provides an additive for resins, particularlyof the halogenated type, which will provide a highly beneficial effecton the fire retarding abilities of the resin without producing animpairment of the other desirable properties of the resins.

As was stated, the additives of the present invention are particularlyuseful with halogen containing plastic compositions. For example, thehalogen containing polyesters are more flame resistant than thenonhalogenated polyesters. However, the flame resistance of even ahalogenated polyester is not sufficient for some uses, such as inbuildings. Antimony trioxide has been incorporated into such polyesterresins in an attempt to increase the flame resistance of the resins.Also, chlorinated paraffin wax has been added to polyesters.Unfortunately, the addition of antimony trioxide in sufficient quantityto render the halogenated polyester substantially flame resistant hasbeen found to have an adverse effect on the appearance of thehalogenated polyester resin. Further, the addition of the chlorinatedparaffin wax has been found to have a detrimental effect on otherdesirable properties of the polyester resin. It has also been suggestedto incorporate tetrachlorophthalic acid or anhydride in the halogenatedpolyester resins to improve their ability to resist fire. However, thesecompositions have only poor flame retardant properties and usuallypossess low stability and low strength characteristics at elevatedtemperatures. Therefore, they are not entirely satisfactory for manyapplications. In like manner, the use of certain organic phosphoruscompounds has been found unsatisfactory.

The additive of the present invention, namely, 2Z- nO-3B O -3'5I-I O, isalso effective in other halogenate resins, for example, polyvinylchloride. The applicable halogenated resin may contain a fairly low torelatively high halogen content; at least about 10 percent andpreferably at least about 15 percent. The zinc borate may be present inan amount of from 0.2 to 50 percent by weight of the total resinformulation, a preferable range is 0.5 to 30 percent by weight of thetotal resin formulation.

Inasmuch as degree of fire retardance is a result of.

carrying out the precepts of the present invention it is propitious toset forth a test procedure for determining the relative and comparativefire retarding abilities contributed to the resin formulation by thezinc borate of the present invention. The test procedure should have thecapability of indicating reproducible results.

A test method utilized is as follows and is depicted as:

INTERMITTENT FLAME TEST PROCEDURE Specimen preparation:

Polymeric material to be tested should be unreinforced or flat glass matreinforced laminate 0.125 X 0.5 X 8 inches. Edges should be smooth andrectangular. Five specimens should be tested for each casting to beevaluated.

Apparatus preparation:

Adjust a Tirrell burner flame to have a 1.5 inch inner blue cone with aflame height of approximately inches. The axis of the burner should beat an angle of from vertical.

Conditions:

Tests should be made under draft-free conditions. Testing procedure:

The specimen is clamped vertically and the tip ofthe inner blue cone ofthe flame is just touching the lower edge of the 0.5 inch dimension ofthe specimen.

The flame is applied to the specimen and then removed according to thefollowing schedule.

When the burning is observed to continue longer than the off time nofurther flame applications should be made to the specimen and the totalburning time after removal of the flame should be recorded. Burning timein excess of 120 seconds should be considered as continuous and recordedas Continuous Burning (C.B.).

Rating:

1. If all of five samples can be carried through all five ignitions andif their burning time after the last ignition does not exceed thespecified maximum time (50 seconds), the rating is 100.

2. lf all five samples exceed the allowed burning time after the firstignition 10 seconds), the rating is 0.

3. If, for instance, two samples carry through three ignitions and threesamples through four ignitions, the rating would be 72.

DETAILED DESCRIPTION To illustrate the invention, a series of exampleswas prepared of a styrenated chlorinated polyester resin, such as Hetron353, a product of Hooker Chemical Corporation, containing about 2325percent chlorine. The resin was divided into batches and labeled asexamples as indicated in the following table. The resin batches werepreaccelerated with a cobalt salt for use with methyl ethyl ketoneperoxide catalyst. The zinc borate of the present invention and otheradditives were stirred into respective batches comprising the examplesuntil a smooth paste was attained. The resultants were de-gassed underoil pump vacuum. Methyl ethyl ketone peroxide at the rate of one partper hundred of resin was then stirred in carefully to avoid introductionof air bubbles. The mixtures were then poured into molds.

The resulting castings were cured at room temperature for approximately12 hours after which they were removed from the mold and post cured for2 hours in a forced air oven maintained at 180F.

The castings were then conditioned for at least 48 hours at F. and 50percent relative humidity. Then the castings were cut into pieces of 8 X0.5 X 0.125 inches and flame tested in accordance with the IntermittentFlame Test Procedure (IFTP) as outlined in the above.

TABLE 1 Examples l-l3 From the above examples it will be noted that thezinc borate having 3.5 moles of water of hydration was compared withantimony oxide and that combinations of the two ingredients were alsoemployed (Example 5 and Example 6).

It will be appreciated that the zinc borate having 3.5 moles waterimproves the fire rating of the polyester resin and generallyaccomplishes this more efficaciously than antimony oxide.

As a means of further demonstrating the advantages of the presentinvention other examples were prepared involving polyvinyl chloride insheet form. The sheets were prepared in the manner described below:

A solution of epoxidized soybean oil (0.05 parts), and liquidbarium-cadmium stabilizer (0.02 parts) in di-(2-ethyl-hexyl)-phthalateplastisizer (0.5-0.6 parts) was prepared. Vinyl chloride homopolymer (1part) was added portion-wise to this slowly stirred solution.

When a homogenous mixture was obtained, the entire mass was deaeratedunder oil pump vacuum.

Individual sheets (approx. 8 X 8 X 0.125 inches) were prepared by addingthe selected fire retardants as indicated in Examples l4-2l to 200 g. ofplastisol stock, mixing well, deaerating and pouring into a glass mold.The plastisol was cured by heating the mold in a forced air oven at350F. for 45 minutes.

After storing for at least 48 hours at 70F. and 50 percent relativehumidity, the sheets were cut into strips 8 X 0.5 X 0.125 inches andtested by the lFTP test described above and by the Globar flame testmethod ASTM D-757.

The effectiveness of various zinc borates as fire retardant additivesfor polyvinyl chloride plastisols, particularly Geon l2l vinyl chloridehomopolymer, is demonstrated below in the Examples 14-25. It will benoted that the examples include a comparison between 22- nO'3B -3.5H Oand 2ZnO'3B O 7H O. Example 24 also shows a mixture of antimony oxideand the zinc borate. From the examples, it will be discerned that thezinc borate having 3.5 moles of water of hydration lowers the burn rateof the polyvinyl plastisol and makes it self-extinguishing.

TABLE I1 Globar Flame Test Examples 14-22 Ex. Fire Retardant 72 by S. E.time Burn rate No. Weight (min) in./min. 14 Antimony oxide 9 1.1 0.28 152ZnO3B,O '3.5H O 2.4

Antimony oxide 2.4 1.8 0.23 16 2Zn0-3B,O;,-3.5H O 3.2 Antimony oxide 0.8Chlorowax 500 15.3 1.9 0.27 17 2ZnO-3B,O 7H O 4 Chlorowax 500 15.3 1.90.37 18 2ZnO-3B,O;,'3.5H,O 16.6 2.2 0.43 19 Antimony oxide 2 Chlorowax500 15.6 2.3 0.29 20 2ZnO3B O -,7H O 16.6 2.4 0.47 21 Chlorowax 500 15.9N.S.E.* 0.47 22 Control N.S.E.* 0.52

*N.S.E. not self-extinguishing TABLE I11 PVC Castings lFTP Test Ex. FireRetardant by lFlP Weight Rating 23 None 0 16 24 Antimony oxide 2.5 80

2ZnO'3B O;,3.5H O 2.5 25 Antimony oxide 5.0 68

In a modification of the test procedure, the following examples are setforth to show results of deterioration of polyvinyl chloride under theinfluence of heat which is maintained for a period to time as indicatedin Table 111. Various zinc borates were employed, showing a comparisonbetween 3.5 moles of water, 7 moles of water and 9 moles of water, alongwith or without various other additives, such as Chlorowax 500, achlorinated paraffin.

TABLE IV PVC Plastisols Heat Stability Study At 350F.

Examples 26-33 nc No Change The effect of the zinc borate of the presentinvention on the physical properties of polyvinyl chloride plastisols,including elongation and tensile strength is illustrated in thefollowing examples wherein zinc borates of 3.5 moles of water, 7 molesof water and 9 moles of water were compared, as well as a comparisonwith antimony oxide.

TABLE V Examples 34-38 Ex. Fire by Stress at Tensile Elong- No.Retardant wt. 100% elong- Strength ation(%) ation(psi) (psi) None 680840 2ZnO-3B O 9H O 9 640 910 antimony oxide 4.7 660 780 130 Two otherstandard tests which can be used in assessing the effectiveness of thezinc borate as a fire retardant are ASTM E-l62 (also known as theNational Bureau of Standards Radiant Panel Test) and ASTM D2863-3O (alsoknown as the Oxygen lndex Test). Correlation of the results of thesetests as well as the abovedescribed Intermittent Flame Test Procedurewill give a good indication of the fire retardancy of the polymer beingtested. For example, a radiant panel flame spread index of 15 or loweraccompanied by an oxygen index of 35 percent or higher can be said toindicate fire retardance in the Class 1 region. The following is adescription of the Radiant Panel Test.

RADIANT PANEL TEST The equipment includes a 12 by l8-inch radiant heatpanel, a specimen holder, a gas pilot, a stack, and properinstrumentation to assure reproducible test conditions. The radiantpanel is mounted in a vertical position and supplied with a premixedgas-air mixture. Its energy output is maintained constant by a radiationpyrometer. The holder supports a 6 by l8-inch specimen in an inclinedposition so that the top 6-inch edge of the specimen is 4 /2 inches andthe bottom edge 9% inches from the radiant panel. The gas pilot islocated near the top edge of the specimen. The stack, which is locatedabove the specimen, collects heat and products of combustion from theburning specimen and supports the thermocouples for measuring the gastemperatures.

During typical tests the specimen is exposed to the radiant panel for 15min. When sufficiently heated, it is ignited by the gas pilot. The rateof flame movement down the panel is recorded along with stacktemperatures.

The test results reported are a flame spread index which is calculatedfrom the time intervals the flame front arrived at 3-in. positions alongthe length of the specimen, the maximum observed stack temperature riseabove that observed when testing asbestos-cement board, and a constantarbitrarily chosen to yield a flame spread index of approximately 100for red oak. The index is computed in this manner to recognize both theignition and heat evolution characteristics of the material beingtested.

OXYGEN INDEX TEST 1n the Oxygen lndex Test, panels are cut to 5.0 X 0.25X 0.125 inches and placed vertically in the center of a 3 inch diameterglass chimney. The atmosphere in the chimney is controlled by regulatingseparate nitrogen and oxygen inlet flow rates. The specimen is ignitedat the upper end and the nitrogen and oxygen ratio adjusted untilcombustion is just supported. The minimum concentration of oxygenrequired to support combustion is reported as a percentage and thisfigure is defined as the oxygen index.

Several polyester resin test panels were prepared by the followingprocedure:

A flat piece of plywood of three-fourth inch thickness is used as asupport. A layer of Mylar film is placed on the plywood support and onthis are placed two 20 oz. Fiberglas matts. An extremely thin matt ofFiberglas material (veil) is placed on top of the matts and the resinmixture then applied to this composite and worked into the Fiberglas. Asecond sheet of Mylar film is placed on the matt and the matt worked androlled with a roller until smooth. Weight is then applied to the matt byuse of a second piece of plywood, and the matt allowed to cure forseveral hours. After the initial cure, the Mylar film is removed and thespecimen panels cut for curing. The panels are cured at about 200F. for2 hours to give Fiberglas panels which after cutting to size are thenready for fire testing.

The resins tested were Hetron 92 (a chlorinated polyester produced byHooker Chemical Corp. containing 28.5 percent chlorine), Stepan CX7l7 (abrominated polyester produced by Stepan Chemical Company), and achlorinated resin prepared by styrenating a chlorinated polyester baseto give a resin containing 28 percent chlorine. The resins were testedby the radiant panel test, oxygen index test and intermittent flame testdescribed above. The results were as follows:

Additive Amt. lFl'P Flame Oxygen (phr) Spread lndex lndex 71 Hetron 92Control 87 23 30 Stepan CX7 l 7 Control 0 I00 12.5 34

Chlorinated Polyester Control 0 45 28 Antimony oxide 0.5

Antimony oxide 2 Antimony oxide l Antimony oxide 2 80 9.] 37

phr parts additive per hundred parts of resin The present additives maybe used with other polymers in addition to those shown in the aboveexamples, such as chlorinated and brominated epoxy resins,polyvinylidine chloride, chlorinated rubbers, chlorinated polyethyleneand brominated polystyrene as well as non-halogenated polymers, such asthe polyolefins and polyesters, to which have been added halogenatedadditives. Preferably the resins should contain at least 10 percent byweight of halogen.

If desired other additives may be used in addition to antimony oxidewhich may be present in a percentage of up to about 10 percent by weight(zinc borate: antimony oxide weight ratio of about lzl, for example),such as calcium carbonate, silica, sodium bicarbonate, borax, talc,jute, glass fibers, plasticizers, stabilizers, curing agents andaccelerators, as well as pigments.

It is within the scope of the present invention to incorporate otheringredients such as plasticizers, dyes, pigments, fillers, stabilizers,antioxidants, antistatic agents and the like without detracting from theother advantageous properties of the polymers.

Various changes and modifications of the invention can be made and, tothe extend that such variations incorporate the spirit of thisinvention, they are intended to be included within the scope of theappended claims.

What is claimed is:

l. A flame retarding composition comprising a halogenated polymerselected from the group consisting of brominated polyesters, polyvinylchloride plastisols and chlori-nated polyesters, and a flame retardingamount of a zinc borate have the formula 22- nO-3B O 33 to 3.7 H 0.

2. The composition of claim 1 wherein the halogenated polymer is achlorinated polyester.

3. The composition of claim 1 wherein the halogenated polymer ispolyvinyl chloride.

4. The composition of claim 1 wherein the zinc borate is present in theamount of 0.2 to 50 percent by weight of the composition.

5. The composition of claim 1 wherein the zinc borate is present in theamount of 0.5 to 30 percent by weight of the composition.

6. The composition of claim 1 wherein the zinc borate is present in theamount of 2 to 10 percent by weight of the composition.

7. The composition of claim 1 wherein antimony oxide is included in anamount up to and including 10 percent by weight of the composition.

8. The composition of claim 1 wherein the halogenated polymer containsat least 10 percent halogen.

9. The composition of claim 1 wherein halogenated hydrocarbon wax isincluded in an amount up to and including 20 percent by weight of thecomposition.

10. The composition of claim 1 wherein the zinc borate has the formula2ZnO'3B O '35H O.

11. A fire-retarding composition comprising zinc borate of the formula2ZnO'3B O 35H O and antimony oxide.

12. The composition of claim 11 wherein said zinc borate and antimonyoxide are present in a weight ratio of about 1:1.

13. The composition of claim 11 wherein a halogenated hydrocarbon wax isincluded.

14. The composition of claim 13 wherein said halogenated hydrocarbon waxis a chlorinated paraffin.

2. The composition of claim 1 wherein the halogenated polymer is achlorinated polyester.
 3. The composition of claim 1 wherein thehalogenated polymer is polyvinyl chloride.
 4. The composition of claim 1wherein the zinc borate is present in the amount of 0.2 to 50 percent byweight of the composition.
 5. The composition of claim 1 wherein thezinc borate is present in the amount of 0.5 to 30 percent by weight ofthe composition.
 6. The composition of claim 1 wherein the zinc borateis present in the amount of 2 to 10 percent by weight of thecomposition.
 7. The composition of claim 1 wherein antimony oxide isincluded in an amount up to and including 10 percent by weight of thecomposition.
 8. The composition of claim 1 wherein the halogenatedpolymer contains at least 10 percent halogen.
 9. The composition ofclaim 1 wherein halogenated hydrocarbon wax is included in an amount upto and including 20 percent by weight of the composition.
 10. Thecomposition of claim 1 wherein the zinc borate has the formula2ZnO.3B2O3.3.5H2O.
 11. A fire-retarding composition comprising zincborate of the formula 2ZnO.3B2O3.3.5H2O and antimony oxide.
 12. Thecomposition of claim 11 wherein said zinc borate and antimony oxide arepresent in a weight ratio of about 1:1.
 13. The composition of claim 11wherein a halogenated hydrocarbon wax is included.
 14. The compositionof claim 13 wherein said halogenated hydrocarbon wax is a chlorinatedparaffin.